U.S. patent application number 11/655639 was filed with the patent office on 2007-10-25 for in vivo device with balloon stabilizer and valve.
This patent application is currently assigned to Capso Vision, Inc.. Invention is credited to Kang-Huai Wang, Gordon Wilson.
Application Number | 20070249900 11/655639 |
Document ID | / |
Family ID | 38620358 |
Filed Date | 2007-10-25 |
United States Patent
Application |
20070249900 |
Kind Code |
A1 |
Wilson; Gordon ; et
al. |
October 25, 2007 |
In vivo device with balloon stabilizer and valve
Abstract
An in vivo imaging system is provided with a capsule having at
least one balloon configured to orient the capsule in a consistent
orientation relative to an internal organ; at least one valve
configured to control the quantity of gas within the at least one
balloon; and an imager encased within the capsule.
Inventors: |
Wilson; Gordon; (Saratoga,
CA) ; Wang; Kang-Huai; (Saratoga, CA) |
Correspondence
Address: |
Stevens Law GRP
P O Box 1667
San Jose
CA
95109
US
|
Assignee: |
Capso Vision, Inc.
Saratoga
CA
|
Family ID: |
38620358 |
Appl. No.: |
11/655639 |
Filed: |
January 19, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60760794 |
Jan 19, 2006 |
|
|
|
Current U.S.
Class: |
600/116 |
Current CPC
Class: |
A61B 1/00036 20130101;
A61B 1/041 20130101; A61B 1/00082 20130101; A61B 5/073 20130101;
A61B 1/00147 20130101 |
Class at
Publication: |
600/116 |
International
Class: |
A61B 1/00 20060101
A61B001/00 |
Claims
1. An in vivo imaging system comprising: a capsule having at least
one balloon configured to orient the capsule in a consistent
orientation relative to an internal organ; at least one valve
configured to control the quantity of gas within the at least one
balloon; and an imager encased within the capsule.
2. An in vivo system according to 1, further comprising a deflation
valve configured to deflate the at least one balloon upon a
predetermined event.
3. An in vivo system according to claim 2, wherein the event is a
change in pressure.
4. An in vivo system according to claim 2, further comprising a
pressure detector, wherein the at least one deflation valve is
configured to deflate the balloons upon the detection of a change
in pressure.
5. An in vivo system according to claim 3, further comprising a
pressure detector, wherein the at least one deflation valve
configured to deflate the balloons upon a change in pressure by
puncturing a membrane of the valve.
6. An in vivo imaging system according to claim 2, wherein the
deflation valve is a normally opened valve, such that the valve is
held closed when power is applied to the valve, wherein the at
least one balloon is configured to deflate when power is removed
and the valve is opened.
7. An in vivo imaging system according to claim 2, wherein the
deflation valve is a normally opened valve, such that the valve is
held closed by a mechanism applied to the valve, wherein the at
least one balloon is configured to deflate when the mechanism is
removed and the valve is opened.
8. An in vivo imaging system according to claim 2, wherein the
deflation valve is a normally opened valve, such that the valve is
held closed by a mechanism when power is applied to the valve,
wherein the at least one balloon is configured to deflate when
power is removed and the valve is opened.
9. An in vivo imaging system according to claim 2, wherein the
deflation valve includes a membrane, such that the membrane seals
the at least one balloon closed, wherein the at least one balloon
is configured to deflate when the membrane is ruptured.
10. An in vivo imaging system according to claim 2, further
comprising a pair of balloons located at opposite ends of the
capsule, and at least one release valve configured to actuate when
a predetermined balloon pressure is detected to deflate the
balloons upon the occurrence of the predetermined pressure.
11. An in vivo imaging system according to claim 10, further
comprising a release valve configured to puncture a barrier when a
predetermined balloon pressure is detected to deflate the balloons
upon the occurrence of the predetermined pressure while traveling
through an organ.
12. An in vivo imaging system according to claim 10, further
comprising a release valve configured to automatically puncture a
barrier [membrane of FIG. 3] to deflate the balloons upon the
occurrence of the predetermined pressure while traveling through an
organ.
13. An in vivo imaging system according to claim 2, further
comprising balloons located at opposite ends of the capsule, a
motion detector, and a release valve configured to deflate the
balloons when the motion detector determines that the capsule has
not progressed significantly for a predetermined period of
time.
14. An in vivo imaging system according to claim 2, further
comprising a motion detector and a release valve configured to
deflate the at least one balloon when the motion detector
determines that the capsule has not progressed significantly over
the course of some number of sequential image captures.
15. An in vivo imaging system according to claim 2, further
comprising a release valve configured to deflate the at least one
balloon when the motion detector determines that the capsule has
not progressed over the course of a predetermined number of
sequential image captures.
16. An in vivo imaging system according to claim 1, further
comprising an inflation valve, wherein the at least one balloon is
configured to expand when the inflation valve is actuated to
stabilize the orientation of the capsule while traveling through
the internal organ.
17. An in vivo system according to claim 16, wherein the inflation
valve is a mechanism configure to release an expansive substance to
inflate the at least one balloon when the mechanism is
actuated.
18. An in vivo system according to claim 17, wherein the expansive
substance is a liquid.
19. An in vivo system according to claim 17, wherein the expansive
substance is a gas.
20. An in vivo system according to claim 17, wherein the expansive
substance is a combination of liquid and gas.
21. An in vivo system according to claim 17, wherein the mechanism
is a membrane.
22. An in vivo system according to claim 21, further comprising an
electrical element configured to remove the membrane to release a
substance to inflate the at least one balloon.
23. An in vivo imaging system according to claim 16, wherein the
capsule is configured to capture images while traveling through a
gastrointestinal track, where the in vivo camera system operates in
a first confined mode while traveling through the small intestine
and in a second expanded mode while subsequently traveling through
the colon, wherein the at least one balloon is configured to expand
when the deflation valve is activated by the occurrence of an event
at two ends of the capsule to stabilize the orientation of the
capsule while in the large intestine.
24. An in vivo imaging system according to claim 1, further
comprising two balloons located at opposite ends of the capsule and
configured to inflate at opposite ends of the capsule using a phase
transition that is activated upon the occurrence of an event, where
the valve is configured to initiate the phase transition and to
inflate the balloons to stabilize the orientation of the
capsule.
25. An in vivo imaging system according to claim 24, wherein prior
to inflation the system includes a vial containing a solution such
that the total vapor pressure of the solution is substantially
equal to a predetermined value, such that the balloon pressure upon
inflation with vapor will not exceed this predetermined value.
26. An in vivo imaging system according to claim 24, wherein the
system further includes a vial containing a substance that, when
released by the valve upon an event, causes the balloon to expand
to a predetermined pressure according to the substance
characteristics and the balloon architecture.
27. An in vivo imaging system according to claim 26, wherein the
event is the expiration of a predetermined amount of time.
28. An in vivo imaging system according to claim 26, wherein the
event is the reception of a remote actuation signal.
29. An in vivo imaging system according to claim 24, further
comprising at least one reserve configured to store an expandable
gas and an electronic balloon actuator configured to cause the
valve to release the expandable gas from the reserve to inflate the
balloons located at opposite ends of the capsule.
30. An in vivo imaging system according to claim 24, further
comprising at least one reserve configured to store a mixture of
substances that is at least partially in the liquid state, wherein
the balloon actuator is configured to cause the valve to release at
least one substance from the reserve to inflate the balloons
located at opposite ends of the capsule, wherein at least a portion
of the substance released vaporizes.
31. An in vivo imaging system according to claim 24, wherein the
balloons are configured to inflate at opposite ends of the capsule
using a chemical reaction that is activated upon the occurrence of
an event to open one or more valves to mix the chemicals in the
balloon and initiate the chemical reaction that generates a gas to
expand the balloons and to stabilize the capsule.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a camera capsule having a miniature
camera for providing images of the digestive tract.
[0002] Devices for imaging body cavities or passages in vivo are
known in the art and include endoscopes and autonomous encapsulated
cameras. Endoscopes are flexible or rigid tubes that pass into the
body through an orifice or surgical opening, typically into the
esophagus via the mouth or into the colon via the rectum. An image
is formed at the distal end using a lens and transmitted to the
proximal end, outside the body, either by a lens-relay system or by
a coherent fiber-optic bundle. A conceptually similar instrument
might record an image electronically at the distal end, for example
using a CCD or CMOS array, and transfer other image data as an
electrical signal to the proximal end through a cable. Endoscopes
allow a physician control over the field of view and are
well-accepted diagnostic tools. However, they do have a number of
limitations, present risks to the patient, are invasive and
uncomfortable for the patient, and their cost restricts their
application as routine health-screening tools.
[0003] Because of the difficulty traversing a convoluted passage,
endoscopes cannot reach the majority of the small intestine and
special techniques and precautions, that add cost, are required to
reach the entirety of the colon. Endoscopic risks include the
possible perforation of the bodily organs traversed and
complications arising from anesthesia. Moreover, a trade-off must
be made between patient pain during the procedure and the health
risks and post-procedural down time associated with anesthesia.
Endoscopies are necessarily inpatient services that involve a
significant amount of time from clinicians and thus are costly.
[0004] An alternative in vivo image sensor that addresses many of
these problems is capsule endoscopy. A camera is housed in a
swallowable capsule, along with a radio transmitter for
transmitting data, primarily comprising images recorded by the
digital camera, to a base-station receiver or transceiver and data
recorder outside the body. The capsule may also include a radio
receiver for receiving instructions or other data from a
base-station transmitter. Instead of radio-frequency transmission,
lower-frequency electromagnetic signals may be used. Power may be
supplied inductively from an external inductor to an internal
inductor within the capsule or from a battery within the
capsule.
[0005] An early example of a camera in a swallowable capsule is
described in the State of Israel, Ministry of Defense Pat. No.
5,604,531. A number of patents assigned to Given Imaging describes
more details of such a system, using a transmitter to send the
camera images to an external receiver. Examples are U.S. Pat. Nos.
6,709,387 and 6,428,469. There are also a number of patents to
Olympus describing similar technology. For example, Olympus U.S.
Pat. No. 4,278,077 shows a capsule with a camera for the stomach,
which includes film in the camera. Olympus U.S. Pat. No. 6,939,292
shows a capsule with a memory and a transmitter.
[0006] An advantage of an autonomous encapsulated camera with an
internal battery is that measurements may be made with the patient
ambulatory, out of the hospital, and with moderate restriction of
activity. The base station includes an antenna array surrounding
the bodily region of interest and this array can be temporarily
affixed to the skin or incorporated into a wearable vest. A data
recorder is attached to a belt and includes a battery power supply
and a data storage medium for saving recorded images and other data
for subsequent uploading onto a diagnostic computer system.
[0007] A common diagnostic procedure involves the patient
swallowing the capsule, whereupon the camera begins capturing
images and continues to do so at intervals as the capsule moves
passively through the cavities made up of the inside tissue walls
of the GI tract under the action of peristalsis. The capsule's
value as a diagnostic tool depends on it capturing images of the
entire interior surface of the organ or organs of interest. Unlike
endoscopes, which are mechanically manipulated by a physician, the
orientation and movement of the capsule camera are not under an
operator's control and are solely determined by the physical
characteristics of the capsule, such as its size, shape, weight,
and surface roughness, and the physical characteristics and actions
of the bodily cavity. Both the physical characteristics of the
capsule and the design and operation of the imaging system within
it must be optimized to minimize the risk that some regions of the
target lumen are not imaged as the capsule passes through the
cavity.
[0008] Two general image-capture scenarios may be envisioned,
depending on the size of the organ imaged. In relatively
constricted passages, such as the esophagus and the small
intestine, a capsule which is oblong and of length less than the
diameter passage, will naturally align itself longitudinally within
the passage. Typically, the camera is situated under a transparent
dome at one (or both) ends of the capsule. The camera faces down
the passage so that the center of the image comprises a dark hole.
The field of interest is the intestinal wall at the periphery of
the image
[0009] FIG. 1 illustrates a capsule camera in the prior art. The
capsule 100 is encased in a housing 101 so that it can travel in
vivo inside an organ 102, such as an esophagus or a small
intestine, within an interior cavity 104. The capsule may be in
contact with the inner surfaces 106,108 of the organ, and the
camera lens opening 110 can capture images within its field of view
112. The capsule may include an output port 114 for outputting
image data, a power supply 116 for powering components of the
camera, a memory 118 for storing images, image compression 120
circuitry for compressing images to be stored in memory, an image
processor 122 for processing image data, and LEDs 126 for
illuminating the surfaces 106,108 so that images can be captured
from the light that is scattered off of the surfaces.
[0010] It is desirable for each image to have proportionally more
of its area to be intestinal wall and proportionally less the
receding hole in the middle. Thus, a large FOV is desirable. A
typical FOV is 140.degree.. Unfortunately, a simple wide-angle lens
will exhibit increased distortion and reduced resolution and
numerical aperture at large field angles. High-performance
wide-angle and "fish-eye" lenses are typically large relative to
the aperture and focal length and consist of many lens elements. A
capsule camera is constrained to be compact and low-cost, and these
types of configurations are not cost effective. Further, these
conventional devices waste illumination at the frontal area of
these lenses, and thus the power use to provide such illumination
is also wasted. Since power consumption is always a concern, such
wasted illumination is a problem. Still further, since the
intestinal wall within the filed of view extends away from the
capsule, it is both foreshortened and also requires considerable
depth of field to image clearly in its entirety. Depth of field
comes at the expense of exposure sensitivity.
[0011] The second scenario occurs when the capsule is in a cavity,
such as the colon, whose diameter is larger than any dimension of
the capsule. In this scenario the capsule orientation is much less
predictable, unless some mechanism stabilizes it. Assuming that the
organ is empty of food, feces, and fluids, the primary forces
acting on the capsule are gravity, surface tension, friction, and
the force of the cavity wall pressing against the capsule. The
cavity applies pressure to the capsule, both as a passive reaction
to other forces such as gravity pushing the capsule against it and
as the periodic active pressure of peristalsis. These forces
determine the dynamics of the capsule's movement and its
orientation during periods of stasis. The magnitude and direction
of each of these forces is influenced by the physical
characteristics of the capsule and the cavity. For example, the
greater the mass of the capsule, the greater the force of gravity
will be, and the smoother the capsule, the less the force of
friction. Undulations in the wall of the colon will tend to tip the
capsule such that the longitudinal axis of the capsule is not
parallel to the longitudinal axis of the colon.
[0012] Also, whether in a large or small cavity, it is well known
that there are sacculations that are difficult to see from a
capsule that only sees in a forward looking orientation. For
example, ridges exist on the walls of the small and large intestine
and also other organs. These ridges extend somewhat perpendicular
to the walls of the organ and are difficult to see behind. A side
or reverse angle is required in order to view the tissue surface
properly. Conventional devices are not able to see such surfaces,
since their FOV is substantially forward looking. It is important
for a physician to see all areas of these organs, as polyps or
other irregularities need to be thoroughly observed for an accurate
diagnosis. Since conventional capsules are unable to see the hidden
areas around the ridges, irregularities may be missed, and critical
diagnoses of serious medical conditions may be flawed. Thus, there
exists a need for more accurate viewing of these often missed areas
with a capsule.
[0013] FIG. 2 shows a relatively straightforward example where the
passage 134, such as a human colon, is relatively horizontal, with
the exception of the ridge 136, and the capsule sits on its bottom
surface 132 with the optical axis of the camera parallel to the
colon longitudinal axis. The ridge illustrates a problematic
viewing area as discussed above, where the front surface 138 is
visible and observable by the capsule 100 as it approaches the
ridge. The backside of the capsule 140, however, is not visible by
the capsule lens, as the limited FOV 110 does not pick up that
surface. Specifically, the range 110 of the FOV misses part of the
surface, and moreover misses the irregularity illustrated as polyp
142.
[0014] Three object points within the field of view 110 are labeled
A, B, and C. The object distance is quite different for these three
points, where the range of the view 112 is broader on one side of
the capsule than the other, so that a large depth of field is
required to produce adequate focus for all three simultaneously.
Also, if the LED (light emitting diode) illuminators provide
uniform flux across the angular FOV, then point A will be more
brightly illuminated than point B and point B more than point C.
Thus, an optimal exposure for point B results in over exposure at
point A and under exposure at point C. For each image, only a
relatively small percentage of the FOV will have proper focus and
exposure, making the system inefficient. Power is expended on every
portion of the image by the flash and by the imager, which might be
an array of CMOS or CCD pixels. Moreover, without image
compression, further system resources will be expended to store or
transmit portions of images with low information content. In order
to maximize the likelihood that all surfaces within the colon are
adequately imaged, a significant redundancy, that is, multiple
overlapping images, is required.
[0015] One approach to alleviating these problems is to reduce the
instantaneous FOV but make the FOV changeable. Patent application
2005/0146644 discloses an in-vivo sensor with a rotating field of
view. The illumination source may also rotate with the field of
view so that regions outside the instantaneous FOV are not
wastefully illuminated. This does not completely obviate the
problem of wasteful illumination, and furthermore creates other
power demands when rotating. Also, this innovation by itself does
not solve the depth of field and exposure control problems
discussed above.
[0016] Alternatively, the capsule may contain a panoramic imaging
system that comprises one or more cameras whose field of view is
directed largely perpendicular to all sides of an oblong capsule so
that a full 360 deg panoramic field of view is covered. A capsule
camera with a panoramic annular lens (PAL) is disclosed in U.S.
application Ser. No. ______, filed on Dec. 19, 2007, entitled In
Vivo Sensor with Panoramic Camera.
[0017] A capsule camera 300 having a panoramic annular lens (PAL)
302, is shown schematically in FIG. 3. The lens 302 has a
concentric axis of symmetry and comprises two refractive surfaces
and two reflective surfaces such that incoming light passes through
the first refractive surface into a transparent medium, is
reflected by the first reflective surface, then by the second
reflective surface, and then exits the medium through the second
refractive surface.
[0018] The capsule camera 300 includes LED outputs 304 configured
to illuminate outside the capsule onto a subject, such as tissue
surface being imaged. The LEDs include LED reflectors 306
configured to reflect any stray LED light away from the lens 302.
The purpose of the LED light rays is to reflect off of the tissue
surface and into the lens 302 so that an image can be recorded. The
reflectors serve to reflect any light from the light source, the
LEDs, away from the lens 302 so that only light rays reflected from
the tissue surface will be imaged. The LEDs are connected to
printed circuit boards PCBs 305 that are connected to each other
via a conductor wire or plate 307, distributing power to each LED.
The lens 302 is configured to receive and capture light rays 308
that are reflected off of an outside surface, such as a tissue
surface, and receives the reflected rays through a first refractor
310. The refracted rays 312 are transmitted to a first reflector
314, which transmits reflected rays 316 onto the surface of a
second reflector 318. The second reflector then reflects reflected
rays 320 through a second refractor 322, sending refracted rays 324
through opening 326 and into a relay lens system 327.
[0019] The system shown is a Cooke triplet relay lens, and it
includes a first lens 328 for receiving the refracted rays 324 from
the second refractor 322. The first lens focuses the light rays 330
onto a second lens 332. Those focused rays 334 are sent to third
lens 336, which focuses rays 338 onto sensor 340. The sensor is
mounted on PCB 342, which is connected to the capsule outer walls
344.
[0020] The capsule 300 further includes electrical conductor 346
connecting the PCB 342 holding the sensor to the conductor plate or
wire 307. The electrical conductor 346 is configured for powering
the LEDs 304 through the conductor plate 307 and PCBs 305 that hold
the LEDs 304.
[0021] The PAL lens 302 produces an image with a cylindrical FOV
from a point-of-view on the concentric axis. A relay image system
after the PAL lens 302 forms an image on a two-dimensional light
sensor 340 that may be a commonly known sensor such as a CMOS or
CCD array. FIG. 3a illustrates a Cooke triplet relay lens 327.
There exists other configurations that are well known in the art
and include double-Gauss configurations.
[0022] A capsule camera with a panoramic imaging system comprising
multiple cameras with overlapping fields of view is disclosed in
co-pending and commonly assigned U.S. application Ser. No. ______
filed on Jan. 19, 2007, entitled System and Method for In Vivo
Imager with Stabilizer, and illustrated in FIG. 4. FIG. 4
illustrates 2 cameras 404, 406 that share a common image plane 408,
but through the action of prisms 410 that fold the optical axes of
each camera, have FOVs 409 that are substantially perpendicular to
the longitudinal axis 411 of the camera. By combining a sufficient
number of such cameras, such as four, the FOVs 409 may overlap so
that a full 360 deg FOV about the capsule is covered.
Adventitiously, the cameras may share a common image sensor 408
since the images are coplanar, and each can transfer images on
their respective sensor areas 418, 420. The image sensor is
configured to receive images projected on it by prisms 410, 412 and
414,416 onto image space 418,420. Image processor 422 is configured
to process the images using well known processing techniques, such
as storage and other processes. Image compressor 424 is configured
to compress images so that less information and thus less power is
required to transmit the image data. Memory 426 is for storing
image data, power 428 is typically a battery for powering the
components, and input/output is configured for sending image data
and possibly receiving relevant data.
[0023] Because panoramic imaging systems capture images of an organ
with a field of view substantially perpendicular to the tissue
surface, they more readily obtain high resolution, evenly exposed,
images of the organ tissues than do systems whose FOVs are centered
in the forward or backward direction. Furthermore, panoramic images
are more readily stitched together to form a continuous image
because consecutive images captured as the capsule traverses the
organ are more similar in terms of both exposure and parallax. Even
without utilizing true image stitching, panoramic imaging systems
facilitate image processing algorithms that reduce the number of
redundant images that are stored in the capsule or transmitted
wirelessly from the capsule by comparing consecutive images.
[0024] In spite of these advantages, a capsule camera with a
panoramic imaging system still encounters a number of challenges in
a large organ such as the colon. If the length of the capsule is
less than the width of the colon, then the capsule's orientation is
not well controlled and it may even tumble as it progresses through
the organ. When the capsule's longitudinal axis is not parallel to
the longitudinal axis of the colon, the panoramic camera's FOV will
not be as nearly perpendicular to the wall of the colon, resulting
in increased parallax. Furthermore, even when oriented
longitudinally, the capsule will typically not be centered in the
lumen so that some portions of it are closer to the camera than
others. In order to maintain proper focus over a range of object
distances, a number of techniques to increase the depth of field
are well known. The F/# of the imaging system may be reduced.
However, this reduces the diffraction-limited resolution of the
system and also requires more illumination to achieve proper
exposure. A mechanism for controlling the focus may be included,
but the focus must be controlled independently for different
viewing directions. One might utilize a plurality of cameras with
different FOVs that each have an autofocus mechanism. However, such
an approach will add cost, complexity, and power consumption to the
system. Finally, techniques such as "wavefront coding" combine an
optical filter with image post-processing to increase the
depth-of-field. However, these techniques do add noise to the image
during post-processing and thereby reduce the dynamic range.
[0025] An additional challenge for a capsule camera in the colon is
exposure, which, for a camera without a shutter or settable
aperture, becomes a problem of illumination. The side of the
capsule that is farthest from the lumen wall must produce
substantially more illumination than the side that is closest.
While illumination about the capsule is more easily controlled than
focus, spurious reflections within the capsule of a bright
illumination source are more likely to produce noticeable artifacts
in the image. Thus, it is desirable to limit the distance between
the capsule and the lumen wall.
[0026] Finally, a variable capsule-to-tissue distance means that a
frame capture rate sufficient to minimize the chance of missing
tissues that are close to or touching the capsule will typically
result in images of tissues that are farther from the capsule
containing redundant information in consecutive images.
[0027] All of the aforementioned problems are mitigated if the
capsule is maintained in the center of the colon with an
orientation aligned to its direction of motion along the colon. One
means of stabilizing the colon is disclosed in US patent
application US2006/0178557 which describes a capsule with sacks of
clay attached to either end. These sacks are covered with a smooth
sacrificial layer when the capsule is swallowed, and the
sacrificial layer remains intact until dissolved by the action of
bacteria upon entering the colon, at which time the clay absorbs
water and expands. The overall shape of the system is thus like a
dumbbell and the central cylinder of the capsule is suspended in
the center of the colon. The application suggests that a plurality
of cameras be included in the capsule, each with a different
orientation, so that a 360 deg FOV is covered.
[0028] While such a system could effectively stabilize the capsule,
it has a number of shortcomings. First, a viable means of panoramic
imaging is not disclosed. Given the space constraints, no more than
one, or at most two, independent conventional cameras can be fit
into the capsule. A system that utilizes the expansion of clay upon
hydration also suffers from some potential safety issues. First, if
the sacks expand prematurely in the small bowel they may place too
much pressure on the organ tissues resulting in eschemia and no
means of controlling the size or pressure exerted by the sacks is
disclosed. Furthermore, no means of reducing the size of the sacks
once they have expanded is disclosed. Thus, they may become stuck
behind the ileo-cecal valve, should they deploy accidentally in the
small bowel, or behind a constriction in the colon that may exist
due to an abnormality, or finally they may be difficult to pass
through the rectum out of the body.
[0029] Thus there exists a need in the art for a more improved
system and method for stabilizing a swallowable capsule camera
system for safe and effective in-vivo viewing of internal organs
such as the colon that are large relative to the diameter of a
capsule that is easily swallowed.
[0030] Such systems described in these co-pending and commonly
assigned applications however, can be improved with an improved
mechanism for controlling the inflation and deflation of the
balloons while in operation, taking images from within a patient's
GI track. As will be seen below, the invention provides such a
system and a method that overcomes the problems of the prior art,
and they do so in an elegant manner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a drawing of a capsule within a small body organ
cavity such as the small intestine according to the invention;
[0032] FIG. 2 is a drawing of a capsule within a large body organ
cavity such as the large intestine according to the invention;
[0033] FIG. 3 is a drawing of a capsule according to the
invention;
[0034] FIG. 4a is a drawing of a capsule according to the
invention;
[0035] FIGS. 4c,d are graphs;
[0036] FIG. 5 is an embodiment of a plug valve according to the
invention;
[0037] FIG. 6 is an embodiment of a capsule FIG. 3 is a drawing of
a capsule according to the invention;
[0038] FIG. 7 is an embodiment of a capsule FIG. 3 is a drawing of
a capsule according to the invention;
[0039] FIG. 8 is an embodiment of a capsule FIG. 3 is a drawing of
a valve according to the invention;
[0040] FIGS. 9-10g are flow charts of methods of the invention;
[0041] FIG. 11 is a view of two images capture showing overlap;
and
[0042] FIG. 12 is an example of an image projection from a
panoramic camera.
DETAILED DESCRIPTION
[0043] The invention is directed to an in vivo imaging system
configured in a capsule for capturing images as the capsule travels
through internal organs, such as the gastro intestinal (GI) track.
Typically the capsule is cylindrical in shape, with rounded ends
much like a vitamin or other pill that can be swallowed. Such a
capsule can be swallowed by a patient for examination, and the
capsule can capture images with its built-in imager, such as a
camera, as it travels through the GI track. In smaller organs, such
as the esophagus or the small intestine, the capsule can be
relatively easily oriented, where the capsule can maintain a steady
orientation while traveling through these smaller organs. In larger
organs, however, the orientation can become unsteady, where the
focal distance between the imager and the tissue being observed can
widely vary, and the images can become distorted when capture and
later observed by a doctor or other medical professional. Thus,
stability is needed in larger organs.
[0044] For stability in larger organs, such as the large intestine,
the invention provides a novel feature, where capsule has at least
one expandable balloon configured to orient the capsule in a
consistent orientation relative to an internal organ. In one
embodiment, the capsule has two expandable balloons located at
opposite ends of the capsule. Thus, when the capsule enters an
organ that has an internal open space that is large relative to the
size of the capsule, the balloons can be expanded to better fit the
space. Different embodiments of balloons can be configured for this
purpose, and several such configurations are possible. For example,
co-pending U.S. patent application Ser. No. ______, filed Dec. 19,
2006, discloses several embodiments of capsules having expandable
balloons. These balloons, however, require a save and useful means
for controlling the inflation and deflation of the balloons. If a
capsule were to be deployed and the balloons were expanded in the
wrong location, there could be problems with blockage, discomfort,
or other injury to the patient, and surgery may even be required.
The invention provides a novel method of controlling the inflation
and deflation of the balloons. In order for the capsule to operate
properly with an expandable balloon, a novel valve system and
method are provided to inflate and deflate the balloon while in
use.
[0045] As described herein, a valve is a broad term that is meant
to describe a barrier between two volumes, such as between the
inside and outside of the capsule, that can be opened or removed by
providing a signal to, or by apply electrical power to or removing
electrical power from, an actuator that controls the valve. The
valve may help to contain in a vial or other container an
expandable material, such as a liquid that can expand into a vapor
to inflate the balloons when the valve is opened. Alternatively, a
valve may also be used to deflate the balloons at the desired
moment or capsule location within the body. Different embodiments
of valves are illustrated and described herein, and are intended
only as examples, embodiments of the invention, and are not
intended to limit the invention. The spirit and scope of the
invention is embodied in the appended claims and their
equivalents.
[0046] In one embodiment, the capsule includes at least one valve
configured to control the quantity of gas or other inflating
material within the at least one balloon so that it can operate
properly, inflating at the correct time, and deflating when desired
or needed. For imaging, an imager encased within the capsule for
capturing images as the capsule travels through the gastro
intestinal (GI) track.
[0047] In one embodiment, a deflation valve is configured to
deflate the balloon or balloons upon a predetermined event. The
event may be a change in pressure, where the deflation valve is
configured to deflate the balloons upon the detection of a change
in pressure. The invention may include a pressure detector. The
deflation valve may be configured to deflate the balloon upon a
change in pressure by puncturing a membrane within the valve. The
deflation valve may be a normally-open valve, such that the valve
is held closed when power is applied to the valve, wherein the
balloon is configured to deflate when power is removed and the
valve is opened. A particular configuration may include one or more
balloons, and may be a pair of balloons located at either end of
the capsule. As such, one or more valves may be incorporated into
the capsule for deflating purposes. One valve may be used to
control the deflation of all balloons if more than one are
employed. Alternatively, each balloon may have an independent valve
to deflate separately. The particular configuration would depend on
the desired features or specifications of a capsule
application.
[0048] The valve may held closed by a mechanism applied to the
valve, wherein the at least one balloon is configured to deflate
when the mechanism is removed and the valve is opened. The valve
may be held closed by a mechanism applied to the valve, wherein the
at least one balloon is configured to deflate when the mechanism is
removed and the valve is opened. The deflation valve may include a
membrane, such that the membrane seals the balloon closed, wherein
the balloon is configured to deflate when the membrane is ruptured.
A pair of balloons may be located at opposite ends of the capsule,
and at least one release valve may be configured to actuate when a
predetermined balloon pressure is detected to deflate the balloons
while traveling through an organ. The release valve may be
configured to automatically puncture a barrier, such as the
membrane of FIG. 3 discussed below, to deflate the balloons upon
the occurrence of the predetermined pressure while traveling
through an organ.
[0049] A capsule may include balloons located at opposite ends of
the capsule, a motion detector, and a release valve configured to
deflate the balloons when the motion detector determines that the
capsule has not progressed significantly for a predetermined period
of time. Image processing techniques can be employed in an imaging
system design, where movement can be detected by capturing and
processing images while moving within an organ. Thus, a motion
detector can determine whether the capsule has progressed
significantly over the course of some number of sequential image
captures.
[0050] In another embodiment of the invention, an alternative valve
may be used as an inflation valve for expanding a balloon or
balloons. The valve may be the same type of valve as the deflation
valve, and may even be the same valve in some configurations. It
may also be different types of valves with different features or
characteristics that are useful and desired in different
applications. However, the function of the inflation valve is to
connect two or more volumes in order to inflate a balloon or
balloon to produce stabilizers for the capsule. The imaging system
may have such an inflation valve, and also have one or more
balloons configured to expand when the inflation valve is actuated
to stabilize the orientation of the capsule while traveling through
the internal organ. The inflation valve may be a mechanism
configured to release an expansive substance to inflate the at
least one balloon when the mechanism is actuated. The expansive
substance may be a liquid that expands to a gas, it may be a gas
that expands to a larger volume, or it may be a combination of
liquid and gas that can expand to inflate the balloons. The
mechanism may be a membrane. The capsule may include an electrical
element configured to remove the membrane to release a substance to
inflate the at least one balloon. The capsule may be configured to
capture images while traveling through a gastrointestinal track,
where the in vivo camera system operates in a first confined mode
while traveling through a smaller organ, such as the small
intestine, and in a second expanded mode while subsequently
traveling through a large organ, such as through the colon and into
the large intestine. The balloon or balloons may be configured to
expand when the deflation valve is activated by the occurrence of
an event at two ends of the capsule to stabilize the orientation of
the capsule while in the large organ.
[0051] In one embodiment, the system may include two balloons
located at opposite ends of the capsule and configured to inflate
at opposite ends of the capsule using a phase transition. This
phase transition may be a substance changing from a liquid phase to
a gas phase, and may be activated upon the occurrence of an event.
The valve may be configured to initiate the phase transition and to
inflate the balloons to stabilize the orientation of the capsule.
Prior to inflation, the system may include a vial containing a
solution such that the total vapor pressure of the solution is
substantially equal to a predetermined value. The balloon pressure
can increase upon inflation with vapor but will not exceed this
predetermined value. The vial may contain a substance that, when
released by the valve upon an event, causes the balloon to expand
to a predetermined pressure according to the substance
characteristics and the balloon architecture. The event may be the
detection of passage through the colon using image processing
techniques that determine whether images are being captured in a
larger cavity, such as in a large organ like the colon. The event
may also or alternatively be a predetermined amount of time, the
reception of a remote actuation signal, or other event the
application calls for.
[0052] The system may include at least one reserve configured to
store an expandable gas for inflating the balloon. It may also
include an electronic balloon actuator configured to cause the
valve to release the expandable gas from the reserve to inflate the
balloons located at opposite ends of the capsule. The system may
include at least one reserve configured to store a mixture of
substances that is at least partially in the liquid state, wherein
the balloon actuator is configured to cause the valve to release at
least one substance from the reserve. This can cause the system to
inflate the balloons, perhaps located at opposite ends of the
capsule, wherein at least a portion of the substance released
vaporizes. The balloons may be configured to inflate at opposite
ends of the capsule using a chemical reaction that is activated
upon the occurrence of an event to open one or more valves to mix
the chemicals in the balloon and initiate the chemical reaction
that generates a gas to expand the balloons and to stabilize the
orientation of the capsule while moving though an organ.
[0053] The balloon attached to a capsule camera should have a means
of deflating should the balloon malfunction and inflate in the
small bowel prior to passing into the colon. Also, the balloon
should deflate should the pressure exerted by the balloon on
internal organs exceed a safe limit, either due to a restriction in
the organ or a quality-control lapse in balloon manufacturing. The
balloon should also deflate whenever the capsule has remained
stationary for a certain period of time. This may occur if the
balloon is stuck behind the ileo-cecal valve or other constriction
or at the rectum. The balloon should also deflate if the capsule
loses power, either due to malfunction or battery drain. The
deflation can be accomplished by means of a release valve.
[0054] According to the invention, a valve for use in an in vivo
capsule can have many useful characteristics. In one embodiment the
valve is configured to be used only once, such as a membrane that
can be punctured or otherwise ruptured at a desired point in the
process of traveling through the GI track. In capsule type systems,
they are not intended for reuse, particularly given sanitary issues
and reliance requirements. The invention provides such a one-use
valve mechanism as described herein that is reliable and low
cost.
[0055] Since most capsule imaging systems are small, there is a
need to keep the power low. This way, smaller batteries or other
power sources, such as induction power sources, can be used. Thus,
the data transmission, data storage (if any) and valve operations
must be efficient and have low power consumption. The invention
provides different valves that do just that. In one embodiment, an
inflation valve is configured as a normally closed valve, where
power is required to open the valve to inflate the balloons. In
another embodiment, a deflation valve is employed that is normally
open, where power is needed to keep the valve closed. This would
only need to be closed while the balloons are inflated, and power
can be removed when it is desired to deflate the balloons.
[0056] A typical capsule endoscope operates with two 1.6V
batteries, and, optimally, all capsule functions operate with a
supply voltage of 3.2V or less. Otherwise a step-up regulator is
required, which is not 100% energy efficient, and adds to the size,
cost, and complexity of the system. Thus, a valve with low-voltage
actuation is desirable, and the invention provides a means to
operate a valve or valves at low voltage as well as at low
power.
[0057] Since capsule imaging systems are small, there is a need to
keep the power consumption low so that small batteries or other
power sources, such as induction power sources, can be used. Thus,
the valve operations must have low power consumption. Fortunately,
the capsule operates in an environment inside the body that
exhibits minimal temperature variation, so that a valve may be
actuated thermally with minimal power consumption.
[0058] In one embodiment, an inflation valve is configured as a
normally-closed valve, where power is required to open the valve to
inflate the balloons. In another embodiment, a deflation valve is
employed that is normally open, where power is needed to keep the
valve closed while the balloons are inflated. When power is removed
from the valve, it opens and the balloon or balloons deflate.
[0059] A typical capsule endoscope operates with two 1.6V
batteries, and, optimally, all capsule functions operate with a
supply voltage of 3.2V or less. Otherwise a step-up regulator is
required, which is not 100% energy efficient, and adds to the size,
cost, and complexity of the system. Thus, a valve with low-voltage
actuation is desirable, and the invention provides a means to
operate a valve or valves at low voltage as well as at low
power.
[0060] A typical capsule endoscope operates with two 1.6V
batteries, and, optimally, all capsule functions operate with a
supply voltage of 3.2V or less. Otherwise a step-up regulator is
required, which is not 100% energy efficient, and adds to the size,
cost, and complexity of the system. Thus, a valve with low-voltage
actuation is desirable, and the invention provides a means to
operate a valve or valves at low voltage as well as at low
power.
[0061] Since capsule imaging systems are small, there is a need to
keep the power consumption low so that small batteries or other
power sources, such as induction power sources, can be used. Thus,
the valve operations must have low power consumption. Fortunately,
the capsule operates in an environment inside the body that
exhibits minimal temperature variation, so that a valve may be
actuated thermally with minimal power consumption.
[0062] In one embodiment, an inflation valve is configured as a
normally-closed valve, where power is required to open the valve to
inflate the balloons. In another embodiment, a deflation valve is
employed that is normally open, where power is needed to keep the
valve closed while the balloons are inflated. When power is removed
from the valve, it opens and the balloon or balloons deflate.
[0063] A typical capsule endoscope operates with two 1.6V
batteries, and, optimally, all capsule functions operate with a
supply voltage of 3.2V or less. Otherwise a step-up regulator is
required, which is not 100% energy efficient, and adds to the size,
cost, and complexity of the system. Thus, a valve with low-voltage
actuation is desirable, and the invention provides a means to
operate a valve or valves at low voltage as well as at low
power.
[0064] Since the capsule is limited in size, it is also imperative
that the mechanism be very small, so that other components can be
located within the capsule. The invention provides such a miniature
valve mechanism as described herein.
[0065] The particular application of inflating or deflating a
balloon attached to an in vivo capsule camera opens up a number of
valve design options. Unlike valves in many gas handling
applications, this valve need not withstand large pressures or flow
rates. Also, linear flow control is not required (the valve
requires only an open and a closed state, not intermediary
states).
[0066] Various MEMS valves exist, for example from Redwood
Microsystems. However, these are typically designed for repeat
actuation, high pressure, and high flow rates. As such, the power
required is too great for the capsule camera application. The fact
that the valve only needs to operate once opens up a number of
unique design possibilities. One approach would be to create a form
of burst valve where an actuator controls the position of a sharp
stylus. When the stylus is pushed against a membrane, the membrane
bursts, releasing the gas.
[0067] In another embodiment, the release valve consists of a
substrate with one or more holes that are filled by plugs. The
substrate is made of a material such as glass or ceramic with a low
coefficient of thermal expansion (CTE) while the plug is made of a
material such as polymer with a higher CTE. The plug and hole may
both have a taper. In a preferred embodiment, the taper of the plug
exceeds that of the hole. FIG. 4b shows a plot of the diameters of
the hole and of the plug in a particular cross sectional plane for
each part as a function of temperature, assuming no external force
is applied to either the hole or the plug, i.e. when the two parts
are not in contact. As the temperature increases, both the material
in which the hole is formed and the plug expand. At a particular
temperature T0, the diameters are equal. Thus, if the plug is
inserted into the hole with both parts at a temperature T0 using an
infinitesimal force, the plug will stop at a point where the cross
sectional planes defined above for the plug and hole coincide. If a
larger force is applied to insert the plug, the plug may be
inserted a somewhat greater distance, deforming in the process.
[0068] FIG. 4c shows Fd the force required to dislodge the plug
once it has been inserted as a function of the plug's temperature
T. With increasing temperature, the plug will expand faster than
the substrate and the force required to dislodge the plug will
increase. The plug may be inserted into the hole during assembly
with a pre-set force Fset with the assembly at a particular
temperature Tset. In this way, the force needed to dislodge the
plug is set--at a temperature Tset, Fd=Fset+.epsilon., where
.epsilon. is the additional stiction that must be overcome to
dislodge the plug. At other temperatures Fd will vary in a
monotonic predictable fashion as shown in FIG. 4c. It should be
noted that the relationship between Fd and T could vary over time
due to stress induced creep in the parts or due to a change in
.epsilon. the static force of friction (stiction) caused by
corrosion, interdiffusion of material, changes in intermolecular
forces, static electricity, or chemical reactions. Materials and
conditions should be chosen so that these effects are minimized or
occur in a predictable fashion.
[0069] The temperature of the plug may be raised above ambient by
passing a current through a resistive heater proximal to the plug.
If the plug has the appropriate electrical resistance, the plug may
be heated by directly passing current through it. Polymers exist
with a wide variety of electrical conductivities.
[0070] The valve is operated in a normally-open mode in that, with
no heating current, at operating ambient temperature, and with
balloon pressure P1 and ambient pressure P2, where P1>P2, the
force Fg=(P1-P2)A exerted on the plug of area A exceeds the holding
force and the plug will be ejected. However, with sufficient
heating current, the plug heats up and Fg is not sufficient to
dislodge the plug. The minimum temperature required to hold the
plug under a given pressure differential be referred to as the
"stick temperature" Tstick
[0071] In order to minimize power consumption while the valve is
closed, the CTE difference between the plug and substrate should be
as large as possible so that the holding force is a strong function
of temperature. Also, the thermal conductivity of the substrate
should be low and the plug should be thermally insulated as much as
possible. The plug and the heater should have low thermal
resistance between them. Tstick must be chosen above the maximum
ambient temperature expected during operation. Otherwise the valve
will not open. The fact that the range of ambient temperatures for
a valve inside the human body is small limits the maximum
difference between the stick temperature and the ambient
temperature, and thereby the peak power consumption required to
keep the valve closed.
[0072] In order to ensure that the plug remains in place prior to
capsule deployment, when no heating current is applied, a
sacrificial holding layer may be applied to the low-pressure side
of the substrate. This sacrificial layer should be strong enough to
hold the plug in place over the range of shock and vibration that
might be experienced during shipment and handling. It may be
designed to give way with force Fgas if Fgas exceeds the forces
exerted by shock and vibration events. Alternatively, the holding
layer may be dissolved by the fluids in the body after the capsule
is swallowed. However, allowing liquids to come in contact with the
valve will reduce its thermal resistance. The sacrificial layer may
be destroyed by other means such as heating, and fluids can be kept
out with a vent that comprises a gas permeable membrane that blocks
liquid ingress. Alternatively, the plug may adhere to materials on
the high pressure side of the plug and these materials may give way
under the application of Fgas or may be removed by some means prior
to balloon inflation.
[0073] The heater may be a thin film heater on either side of the
plug. FIG. 5 shows a heater with electrodes on either side that
connect the heater to a source of current. The heater may be made
of chromium, tungsten, or some other material of appropriate
electrical resistivity. A temperature sensor such as a thermocouple
may be included near or on the plug as well. A planarization layer
such as spin glass may be placed between the heater and the plug.
In FIG. 1 the planarization layer has been etched away around the
heater and electrodes so that plug is in direct contact with the
gas inside the balloon. Other heater configurations are possible. A
thin film heater may be deposited on the inside wall of the hole,
for example.
[0074] FIG. 6 shows one end of a capsule outfitted with an
elastomer balloon. The balloon is stretched over a rounded porous
support structure and attached at its edges by means of a pressure
fit or epoxy or other means. The balloon and, indeed, the entire
capsule may, in turn, be covered with a layer such as gelatin that
protects the balloon and minimizes the friction of the capsule
during swallowing. The cover material may be chosen to dissolve in
stomach acid or to be breached by bacteria in the small or large
bowel, prior to balloon inflation. After the cover dissolves bodily
fluids may enter the vent and dissolve the sacrificial layer.
Current may either be applied to the heater prior to the cover
dissolving or else just prior to inflating the balloon.
[0075] FIG. 6 shows a balloon inflation mechanism whereby a liquid
or mixture of liquids is held in a vial inside the balloon. When
current is passed through a resistive heater on the vial, the vial
melts at the location of the heater and the liquid vaporizes and
inflates the balloon with vapor. The balloon inflation may be
actuated by other means such as a chemical reaction that produces a
net increase in gas molecules. Alternatively, the balloon may be
initially pressurized but constrained by the cover. When the cover
dissolves, the balloon may deploy passively, without actuation.
[0076] The capsule includes a cover 602 that is to be removed in
the process to allow the elastomer balloon to expand. This may be
done by breaking away when the balloon is released, or by other
means. The capsule includes capsule housing 604, elastomer balloon
606 shown encapsulated in the capsule cover 602. The vapors 608,
FIG. 7, expand to inflate the balloon 606 as the cover releases.
The porous support structure 610 is configured to support the
elastomer balloon in place before deployment, expansion, and also
protects the components from the elastomer balloon, so that there
is no interference with the components. The housing houses the
capsule elements including the sealant for sealing the housing from
vapors and other elements, capsule electronics 632, receptacle 634,
and conductors 636.
[0077] The valve substrate may serve as a printed circuit board
(PCB) on which the electrical connections to the balloon actuator
reside along with the electrical connections to the valve.
[0078] Referring to FIG. 7, an view of the configuration of FIG. 6
is illustrated, where the elastomer balloon is expanded. The
capsule cover 602 does not exist on the expanded FIG. 7, because it
is removed to allow the balloon to expand.
[0079] FIG. 8 illustrates another valve. A thin membrane covers a
hole separating the balloon at pressure P1 from the environment at
pressure P2. Prior to inflation, P1=P2 and the membrane is not
deformed. A sharp stylus is attached to a cantilever bimorph
actuator, such as a thermal bimorph or piezoelectric bimorph. Other
types of actuators could also be used such as electromagnetic,
electrostatic, or thermal-mechanical. When actuated, the actuator
pulls the stylus away from the membrane. When the balloon inflates,
P1>P2 and the membrane deforms toward the stylus. However, if a
critical pressure is not exceeded, the membrane will not reach the
stylus. Now, if the power to the actuator is removed, the stylus
will move into the membrane and burst it so that gas is released
from the balloon through the hole.
[0080] Referring to FIG. 9, one example of a flow process of the
capsule is illustrated in terms of events related to the location
of the capsule in GI track. In the first step 902, the capsule is
ingested. In step 904, it is determined whether the capsule has
entered the stomach. If it has not in step 906, the process returns
to step 904. If it does, then the event is recorded and the process
monitors whether the capsule has entered the colon. If not as
determined in step 910, then the process returns to step 908. Once
it is in the colon, the process goes to step 912 to open the valve,
expanding the balloons. The process ends in step 914.
[0081] By way of example, one method for inflating and deflating
the balloons according to the invention is illustrated in FIG. 10a,
a general process 1000 illustrated in flow chart. In operation, a
capsule is ingested in step 1002. From there, two processes operate
in parallel. In step 1004, image capture occurs, which can occur
throughout the process while the capsule travels throughout the GI
track. At the same time, a series of monitoring processes occurs
beginning with step 1006, where inflation events are monitored. If
an inflation event does not occur as determined in step 1008, then
the process loops back and continues monitoring the events in step
1006. When an event occurs, then the process initiates the
inflation process in 1010, where the balloon or balloons are
inflated. After the balloons are inflated, then the process must
monitor the system to watch for deflation events in step 1012.
Until a deflation event occurs, the process loops back to step
1012, where deflation events continue to be monitored. Once a
deflation event occurs as determined in step 1014, then the
balloons are deflated in step 1016. The process ends in step
1018.
[0082] Referring back, more detailed processes within some of the
individual steps of FIG. 10a are illustrated in FIGS. 10b through
10f. In FIG. 10b, a more detailed process of image capture of step
1004 is illustrated. First, the process monitors movement via
images in step 1020. Then, it is determined whether there was
movement in step 1022. If movement does not occur, then the process
loops back to step 1020 for further monitoring. Once movement
occurs, then the process proceeds to step 1024, where images are
captured. This feature provides for great reduction in images
captured, where images are only captured when there is movement,
greatly reducing redundant images. Thus, the physician or other
medical professional does not need to review as many images as
otherwise required. In step 1026, it is determined whether the end
of the procedure has been reached. If not, then the process returns
to step 1020, where the movement of the capsule is further
monitored, and the process continues. If the end of the procedure
occurs, whether the capsule has completed the process and been
expelled or if it is ended for any other reason, the process ends
at step 1028, which corresponds to step 1018 of FIG. 10a.
[0083] Referring to FIG. 10c, a more detailed illustration of the
step 1014, determining whether a deflation event has occurred, is
shown. In step 1030, the pressure is monitored. This process
monitors pressure as a deflation event, so that the balloon or
balloons would deflate when there is an unsafe increase in
pressure, indicating a blockage of some sort, or perhaps a
premature inflation in a small organ such as the esophagus or a
small intestine, or perhaps the capsule has entered the colon, just
before it enters the large intestine, and it is stuck. If no change
occurs, the process continues to monitor the pressure in step 1030.
If a predetermined pressure level is detected in step 1032, such as
P=P.sub.colon, this indicates that the capsule has incurred a
deflation event in step 1034, and the balloons will be deflated in
step 1016 (FIG. 10a).
[0084] In FIG. 10d, another embodiment of a determination of
whether a deflation event of step 1014 (FIG. 10a) occurs. Here, the
time of movement is monitored in step 1036. Here, it is determined
in step 1038 whether there has been no substantial movement of the
capsule in a person's GI track. If movement occurs, then the
process returns to step 1036 for further monitoring. If, however,
it is determined in step 1038 that enough time has passed to be
concerned, then the process deflates the balloons in step 1040,
which corresponds to step 1016 of FIG. 10a. The process then ends
in step 1018, FIG. 10a.
[0085] Referring to FIG. 10e, an example of a determination of
whether an inflation event, step 1008 of FIG. 10a, occurs is
illustrated. In step 1042, the illumination energy I.sub.E required
to obtain a desired image exposure is measured and monitored. In
step 1043, it is determined whether the capsule is not in the
stomach. If it is in the stomach, the process returns to step 1042
for monitoring. This is useful in preventing premature expansion in
the stomach, preventing a false event indication. In step 1044, it
is determined whether the illumination energy is at a level that
indicates entry of the capsule into the colon, I.sub.Colon. If not,
the monitoring continues in step 1042. Once such an energy is
reached, it is then determined whether the capsule is inside the
small bowel in step 1045, this prevents premature inflation as
well. If not in the small bowel, then the process returns to step
1042. If it is in the small bowel, then it is not likely a false
read. The process then proceeds to the next step where the balloons
are inflated in step 1046, corresponding to step 1010, FIG. 10a,
and the process proceeds to step 1012.
[0086] Referring to FIG. 10f, another example of a determination of
whether an inflation event occurs is illustrated. In step 1048, the
process monitors images captured for colon features. Then, it is
determined whether the capsule is in the stomach. If it is in the
stomach, it returns to step 1048. If not in the stomach, the images
are then compared in step 1050 to known colon images. If there are
no colon images, then the process loops to step 1048 for further
monitoring. then determine If an image of a colon does occur in
step 1050, then it is determined whether the capsule is in the
small bowel. If not in the small bowel, then the process returns to
step 1048 for monitoring. If it is in the small bowel, then the
process inflates the balloons in step 1052.
[0087] Referring to FIG. 10g, the process determines in a different
embodiment whether an inflation event occurs. In step 1055, it is
determined whether the capsule is in the small bowel. If it is not,
then the process goes back until it is in the bowel. Then, the
counter is set to zero in step 1056, and the overlap X between
images capture by the cameras with overlapping FOVs are measured.
In step 1060, it is determined whether the overlap is greater than
a predetermine amount X0. If not, the process returns to step 1056.
If it does, the counter is incremented in step 1062, and it is
determined whether the count exceeds a predetermined count N0. If
it does not, the process returns to step 1058. It does exceed N0,
then the balloons are inflated in step 1066.
[0088] By way of example, FIG. 11 shows a cross section of a
cylindrical capsule. Within the capsule are four cameras. These
cameras may have separate centers of perspective C1, C2, C3, and C4
that lie in the entrance pupils of each camera. Associated with
each camera is also a horizontal field of view HFOV. Each camera
"faces" a different direction such that the optical axes are, in
this case, separated by 90 deg. Since the HFOV of each camera
exceeds 90 deg, the HFOVs overlap. Advantageously, they overlap
along vertical lines within the capsule so that the horizontal
extent of an object touching the capsule on the outside may be
viewed in its entirety.
[0089] Also shown in FIG. 11 is a cross section of the lumen. The
distances from the center of the capsule O to four points on the
lumen wall I, J, K, and L in the plane of cross section are
uniquely determined by the amount of overlap between adjacent
images captured of the lumen. The distance OK is linearly related
to the overlap x.
[0090] FIG. 12 shows two images captured by two adjacent cameras.
The images are placed side-by-side. Only one feature of the images
is shown, a line. This line might correspond to the edge of some
physical feature on the lumen. Due to the non-coincident centers of
perspective and the fact that the line on the lumen is not a
constant distance from the capsule along its vertical extent, the
line has a slightly different shape in the two images. An algorithm
that determines the overlap might first divide the images into a
series of horizontal bands (Four are illustrated in FIG. 12). Each
band could then be translated horizontally until the best image
match is found in the region where the translated bands overlap. In
this simple case, that would occur when the line sections most
overlap. The optimal translation distances (overlaps) for each band
are labeled x1, x2, x3, and x4. Similarly, overlaps and
corresponding object distances can be determined at the other three
overlap regions. By considering a set of data, an estimate of the
cross-sectional area of the lumen can be made. This estimate, along
with previous estimates, can then be used to decide whether the
capsule has entered the colon and whether to deploy the
balloons.
* * * * *